There is an ongoing need for laser and amplifier systems that produce high power while maintaining good output beam quality that can be manufactured at a reasonable cost. Typically, for a diode pumped laser system, pump light from one or more diode pump sources is directed to a solid state gain material that amplifies radiation at a desired wavelength. For such a system, not all of the pump light is converted to desirable radiation amplification; some of the pump light may be converted to heat and some pump light may leak from the system or from one component of the system to another component of the system before being absorbed in the gain material. Such residual leaked pump light from one component of the system to another may be detrimental to the operation of the system. In addition, temperature increases and gradients that result from the heat can lead to detrimental effects on the performance of the system. Examples of such detrimental effects can include bulk thermal lensing, surface bulging and changes to fundamental properties of the laser gain material such as the upper-state lifetime, thermal conductivity and thermal expansion of the material.
Applying pump light of a uniform or substantially uniform density or intensity to the gain material is one way to minimize the negative effects of heat generated by residual unabsorbed pump light. Such an approach usually requires injecting the pump light from multiple sources and directions into the gain material, either directly or indirectly. However, in such systems, there may be crosstalk between the two or more pump sources, particularly if the pump sources are emitting pump energy into the gain material or a conduit, such as an inner cladding of a double clad optical fiber amplifier, from opposite ends of the gain material or conduit. Such cross talk between pump energy sources may lead to feedback and instability in the pump energy sources, particularly in semiconductor lasers that are sensitive to feedback. What has been needed are systems and methods for pumping gain materials from at least two directions while minimizing or eliminating crosstalk and feedback between pump sources. What has also been needed are systems and methods that can produce a high energy output and be manufactured at a low cost.